Combination-controlled and key-operated shackle-type padlocks having a latch bolt spring-biased into locking engagement with the retaining notch formed in the short leg of a U-shaped shackle, are common at the present time. In many prior designs of such padlocks, such as the Patents to Soref et al U.S. Pat. Nos. 2,113,864; 2,487,608; 2,893,231; Check U.S. Pat. No. 3,009,345 and Markert et al U.S. Pat. No. 3,194,033, a spring-biased latch bolt slidably carried in a rocker secures the shackle in a locked position. Moreover, in such key-operated and combination-controlled padlocks, the key cylinder is assembled to the padlock as the complete padlock is assembled. The combination tumblers and key cylinder are enclosed and held in position by a single inner back plate covered by an outer back plate which is held to the lock casing by a rolling operation. Thus, when the padlock is once assembled, the key barrel and cylinder cannot readily be interchanged.
The present invention not only increases the security of the padlock, but overcomes the deficiencies and short-comings of the prior padlocks by providing a two-piece inner back plate accommodating the padlock to be assembled with the tumbler post for the combination tumblers secured to a larger part of the inner back plate which is riveted or otherwise secured to the pivot shaft for the rocker carrying the latch bolt. The padlock may then be stocked with the combination-controlled mechanism assembled to the padlock. The desired key barrel and cylinder may later be selected with the transmission plate for releasing the latch bolt preassembled to the smaller part of the back plate, to be inserted in the padlock casing in a simple and efficient operation. Thus, where the padlock is to be used for schools and the like, a student may open his padlock by dialing the combination dial, and the supervisor for the locker room may open the padlock by a key, where required. A master key may be provided which will open padlocks of various makes and thus make it unnecessary to stock keys for each individual make of padlock.
A further distinction of the present invention over the prior art references listed above is that the latch bolt is always biased to engage the latch bolt receiving notch in the shackle and the rocker carrying the latch bolt is biased to position the latch bolt in a locking position as soon as the padlock is opened and the shackle is disengaged from the latch bolt.
Another advantage of the invention is in the use of biasing means biasing the rocker in position to position the latch bolt to engage the shackle notch, and in the use of a separate spring to bias the latch bolt to engage the latch bolt receiving notch of the shackle.
Still another advantage of the invention is in the simplicity and effectiveness of the padlock attained by combining the transmission plate for releasing the latch bolt, the key cylinder and key barrel, controlling operation of the transmission plate as a unit, assembled to a smaller back plate of a two-piece back plate assembly for the padlock.
A still further advantage of the invention is by constructing the padlock with an inner and outer back plate and making the inner back plate in two pieces, the larger piece of which is held in position by riveting to the pivot shaft for the rocker while the smaller piece is riveted to the key cylinder which carries the key barrel and transmission plate.
A still further advantage of the invention resides in the construction of the padlock to safeguard against opening of the padlock by tapping, or a blow on the shackle.
Another advantage of the invention resides in the unitary mounting of a transmission plate on the key barrel and cylinder and the retention of the transmission plate to the smaller part of the inner back plate of the padlock by the key cylinder.
A still further advantage of the invention is in the arrangement of the upsetting mechanism for the tumblers by locating the upsetting pawl at a more efficient angle than formerly, and by providing an elongated square-cornered tang for the rocker fitting into the aligned slots in the tumblers when the padlock is released by the combination mechanism and retaining the combination dial from rotation upon an outward pull of the shackle relative to the padlock casing.
Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variation and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.